Hey! Today i am going to explain javascript promises and promise chaining with the help of illustrations in this blog.

1. JavaScript Promise

• To manage asynchronous operations,we use Promise.
• It is used to determine whether or not the asynchronous operation was successful.
• Three states of promise are :-
  1. Pending
  2. Fulfilled
  3. Rejected
• A promise is made when it is still pending. That implies that the procedure is not finished.
• The operation concludes in a fulfilled state if it is successful.
• And, the process end in a rejected state,if a error is made.

2. Create a JavaScript Promise

let promise = new Promise (function (resolve, reject){
//do something
});

• We use Promise() constructor to create a promise object.

• The resolve() method is called if the promise is successfully fulfilled.

• The reject() method is called if there is an error.

• Here is an example of an asynchronous program and a promise can be used to manage the program.

3. Promises chaining

• When you need to manage multiple asynchronous tasks sequentially, promises come in handy.

• We use promise chaining for this.

• Using the methods like then( ) and catch( ) you can carry out an action once a promise is fulfilled ( ).

4. then( ) method

• When the promise is properly fulfilled or resolved, the then( ) method is used with the callback.

• The promise allows you to use a chain of multiple then( ) methods.

5. catch( ) method

• When the promise is declined or if an error occurs, the catch( ) function is used with the callback.

6. Promise vs Callback

Javascript Promise

• The syntax is simple to read and understand.

• It is simpler to handle errors.

Javascript Callback

• It's challenging to comprehend the syntax.
• It could be challenging to manage error management.